The disclosure set forth herein relates to a spindle drive conveyor or chain conveyor, as shown for example in U.S. Pat. No. 5,228,557, the entire contents of which are hereby incorporated by reference. In a chain conveyor, as described therein, the belt is entrained and moved by means of drive units each comprising sprockets or toothed wheels engaging with one or both of the chains of the belt, to cause them to move forward at the desired speed. The toothed wheels generally engage the chain tangentially and/or from underneath, and are arranged in a vertical plane passing through the chain.
With reference to FIG. 1, when a conveyor belt 10 is used in a spindle drive conveyor or similar system, tension is carried on the edge 12 of belt 10 by reinforcing bars 14. The wickets 16 on the belt 10 are for product support, rather than taking a load, and the rods 18 are utilized to hold the components of belt 10 together, and to transmit drive forces to the edge 12 of belt 10.
In a straight run, such as the infeed and discharge areas of a helical system, the outer reinforcing bars 14 have little if any effect on the function of belt 10. Drive sprocket teeth 20 (only one of which is illustrated in FIG. 1) engage rods 18 from therebelow and cause rods 18 to deflect at the sprocket tooth 20, releasing tension from the edge 12 of belt 10. This causes wickets 16, whose purpose is for product support, to now take the tension of the belt 10. The sprocket engagement area 22 of rod 18 takes tension from sprocket 20 and applies it to adjacent wicket areas 24 which can lead to wicket fatigue and breakage at one or more of wicket areas 24 where rod 18 meets wickets 16.
In addition, in curved courses of travel, sprockets carried by vertical shafts (of the spindle drive) positively engage the edge 12 of belt 10 when it is collapsed to drive it through each tier of the helix, or through any other curved turn.
Two areas where a flat wire conveyor belt such as shown in FIG. 1 has the most tension is in the sprocket-engagement area 22 of belt 10 and on the edge 12 of belt 10 where it engages the sprockets of the spindle drive. As described in detail in U.S. Pat. No. 7,494,005 to the present assignee, the entire contents of which are hereby incorporated by reference, providing rows of wickets with variable spaced links improves the ability of the conveyor belt to withstand the tension in the sprocket engagement area 22 without fatigue.
Reinforcing bars 14 on the edge of the conveyor belt, as shown in FIG. 1, are used to bear a substantial tractive load. However, the use of reinforcing bars alone has not been entirely successful in eliminating fatigue failures on the positively driven edge 12 of the conveyor belt.
Accordingly, there exists a need in the marketplace for a conveyor belt having an edge configuration for maintaining belt orientation, providing improved positive edge drive capability, and reducing fatigue failures on the driven edges of the conveyor belt.